With the increased awareness of environmental protection, both efficient and environmentally-friendly demands have been put forward on pesticidal formulation. Studies found that for one particular technical material, effect of a pesticidal formulation comprising the technical material depends on the form of the formulation, and dispersion state and size of technical material particles. Scientific knowledge tells us that, when other conditions are identical, the smaller the sizes of technical material particles are, the greater a surface area formed is, and the larger a contact area with plant leaves and pests is. Based on those, a better efficacy will be achieved by the pesticide, and thus the amount of pesticide used will be reduced accordingly.
Standards for evaluating whether a pesticidal formulation is environmentally-friendly or not relate to not only the properties of the technical material itself, but also whether organic solvents are used in the formulation, and whether the solvents and additives used are environmentally-friendly as well. Although various water-based pesticidal formulations are generally environmentally-friendly formulation, how friendly they are to the environment should be evaluated by reference to the above standards.
Among water-based pesticidal formulations, only pesticidal technical material in a water solution (aqueous solution) is dispersed at the level of single molecules, and has minimum size. However, there are only few pesticides that can be processed as aqueous solution and some of them hydrolyze easily in water, which limits the application of aqueous solution in pesticidal formulation. Most pesticides are oil soluble, some of which can only be dissolved in organic solvents, and some of which are even difficult to be dissolved in commonly used organic solvents. Therefore, water-based formulations comprising those pesticides can only be prepared generally into micro-emulsion (ME), emulsion (EW), aqueous suspension concentrate (SC) and aqueous suspo-emulsion (SE). The particle size of pesticidal technical material, when is dispersed in water, increases in turn among the four formulations. Micro-emulsion and emulsion are systems that droplets of pesticidal technical material dissolved in organic solvent are dispersed homogeneously in water; wherein the micro-emulsion has the smallest droplets of lower than 100 nm in size which is less than ¼ of visible light wavelength, thus the micro-emulsion system is transparent and thermodynamically stable. Emulsion has droplets of a few hundred nanometers to microns or above in size, which is close to or even greater than visible light wavelength, thus the emulsion system is opaque and lacks stability. The aqueous suspension concentrate is a system that pesticidal particles, which have been crushed into micron size, are suspended in the water through the action of the macromolecular dispersing agent. This kind of system has a tendency to have pesticidal grains condensed. The aqueous suspo-emulsion is a combination of aqueous suspension concentrate and emulsion. All the above four formulations, expect the aqueous suspo-emulsion, have 10%-20% organic solvent which may reduce their environmental friendliness to different degrees.
Emamectin benzoate (EB) has a structure as shown in formula 2. Emamectin benzoate is a super-effective insecticide and acaricide that is obtained starting from avermectin B1a, one biological antibiotic pesticide, by means of chemical modification. Based on the super-effective, wide-spectral, almost non-toxic, and non-residual advantages, as well as little resistance of emamectin benzoate, the insecticidal activity of it is dozens of times that of the parent avermectin B1a. Results of efficacy experiments show that emamectin benzoate has an activity for many pests that cannot be achieved by other pesticides. Emamectin benzoate is super-effective especially for pests from the orders Lepidoptera and Diptera, and said pests comprise redbanded leafroller, Heliothis virescens, cotton bollworm, Manduca sexta, Plutella xylostella L. Spodoptera littoralis, Spodoptera exigua, Spodoptera frugiperda, Trichoplusis ni (Hubner), Argyrogramma agnata, Pieris rapae Linnaeus, Hellula undalis, Hellula undalis Fabricius, Manduca quinquemaculata, Leptinotarsa decemlineata, Epilachna varivestis and the like. Emamectin benzoate works wonders on resistance cotton bollworm and Plutella xylostella, and it has a good insecticidal effect even at very low doses. Therefore, with the prohibition of use of highly toxic pesticide, emamectin benzoate has become a mainstream product of insecticide on the market.

Emamectin benzoate is easily soluble in various organic solvents, such as acetone, methanol, toluene and xylene, but poorly soluble in water, having a water solubility of only about 0.024 g/L (25° C.). Thus, formulations of emamectin benzoate primarily comprise emulsifiable concentrate (EC), micro-emulsion (ME), emulsion (EW), and water dispersible granule (WG) at present. The mass percentage of active ingredient identified in different formulations is from 0.5% to 5%; wherein the highest content of the effective ingredient is 5.7%, which is equivalent to 5.0% emamectin benzoate.
In the prior art, formulations that use emamectin benzoate as the pesticidal technical material comprise:
Chinese application for invention No. 200710009947.9 discloses a micro-emulsion of emamectin benzoate, wherein components in percentage by weight are: 0.5-5% of emamectin benzoate, 5-20% of solvent, 1-10% of solubilizing assistant, 5-30% of emulsifying agent, 0.1-3% of synergist, 0.1-3% of stabilizer, and the remainder being water; and wherein the solvent is one or more selected from the group consisting of aromatic hydrocarbyl solvents, cyclohexanone, dimethylformamide, and acetone.
Chinese application for invention No. 200510012996.9 discloses an insecticidal micro-emulsion containing emamectin, wherein components are (weight of the micro-emulsion is 100%): 0.2-10% of emamectin, 10-20% of solvent, 8-15% of emulsifying agent, 1-3% of stabilizer, 2-3% of antifreezing agent, and the remainder being water; and wherein the solvent is one or more selected from the group consisting of methanol, ethanol and cyclohexanone.
Chinese invention patent No. ZL200910111224.9 discloses an emulsion of emamectin benzoate, wherein raw materials in the emamectin in percentage by weight are: 0.5-10% of emamectin benzoate, 2-10% of solvent, 2-10% of emulsifying agent, 0.15-5% of co-emulsifying agent, 0.05-5% of thickening agent, 0.2-5% of antifreezing agent, 0.05-0.8% of defoaming agent, and the remainder being water; and wherein the solvent is xylene.
Chinese invention patent No. ZL200610023384.4 provides an emulsion of emamectin benzoate and the preparation method therefor. Substances with following amounts used as raw materials for the emulsion: in percentage by weight, 0.1-20% of emamectin benzoate, 1-10% of solvent, 1-10% of emulsifying agent, 0.1-5% of thickening agent, 0.5-5% of antifreezing agent, 0.1-1% of defoaming agent, and the remainder being water; wherein the solvent is xylene and/or toluene.
In the preparation of the above micro-emulsions and emulsions, organic solvents, such as methanol, toluene, xylene or the mixture thereof and the like which are toxic and harmful are used for dissolving emamectin benzoate, and then emamectin benzoate dissolved in organic solution is dispersed into water through emulsification by surfactants. Although significantly smaller amounts of organic solvents are used in micro-emulsion or emulsion than used in emulsifiable concentrate, the mass percentage of organic solvents is still up to 10%-20%. That is to say, 100-200 kg of organic solvents (such as xylene etc.) would be used when 1 ton of micro-emulsion or emulsion of emamectin benzoate is produced. Organic solvents used could not be ignored when the production scale of those formulations is large, because environmental pollution will come along with spraying the formulations onto crops.
Chinese application for invention with publication No. CN101361479A (publication date: 11 Feb. 2009) discloses a water dispersible granule of emamectin benzoate. Chinese application for invention with publication No. CN1775027A (publication date: 24 May 2006) discloses an insecticidal water soluble granule containing emamectin benzoate.
Emamectin benzoate in dispersible granule and water soluble granule will suspend in water under the action of macromolecular dispersing agent after adding water thereto. However, this kind of system is thermodynamically unstable, and it has a tendency to have grains condensed and precipitation easily occurs after it is allowed to stand for a period of time. What's more, current production process for dispersible granule and water soluble granule has long process flow, including airflow grinding, kneading, granulating and drying etc., for which corresponding production equipments are needed, leading to an increase in production costs.
Moreover, emamectin benzoate itself may degrade rapidly when exposed to light, thus the work period of ordinary pesticidal formulation containing emamectin benzoate is short, generally about 7 days.
Therefore, there is still a need for a novel and more effective environmentally-friendly formulation of emamectin benzoate.